1. Field of Invention
The invention relates to a holding device for a motor vehicle safety means and, more specifically, to a holding device which can be displaced out of a rest position and into an action position.
2. Description of Related Art
Motor vehicle safety means in various versions are known from practice. Such a motor vehicle safety means is used to prevent or limit injury to passengers in case of an accident. Motor vehicle safety means of the type under consideration can include roll bars, movable head supports, knee cushions, displaceable hoods, or the like. In an accident, the motor vehicle safety means is mechanically displaced into a protective position. For this purpose, a corresponding component of the motor vehicle safety means is suddenly displaced out of a rest position into an action position. As a rule, the energy required for this function is made provided by spring elements (e.g., mechanical or pneumatic spring elements).
In normal operation of a motor vehicle, the component which is to be displaced, that is, the component of the motor vehicle safety means, is fixed in its rest position by a holding device where the associated holding forces applied are comparatively high. For operation of the motor vehicle safety means in an accident, reaction time for triggering of the motor vehicle safety should be as short as possible. Whether at any time during the use of a motor vehicle such a case occurs, is however uncertain. It is therefore necessary for the motor vehicle safety means to reliably trigger even after several years of inactivity. Of course, triggering of the motor vehicle safety means should not take place in normal daily operation of the motor vehicle, not even when steering and transverse accelerations, which are typical of operation, occur.
The aforementioned explanations make it clear that contradictory requirements are imposed on a holding device for a motor vehicle safety means. Accordingly, different approaches to construction of these holding devices are known. The known holding device for the motor vehicle safety means which underlies the invention is provided in German Patent Application DE 198 21 594 A1 and which shows a ratchet arrangement for a latch with two ratchets which are arranged to act in succession. The second ratchet represents a blocking element which can be moved by a motorized drive, in this case, by an electromagnet.
In the above described prior art device, the latch, on the one hand, and the two ratchets, on the other, are each arranged at a right angle to one another. The arrangement results in that a force which is triggered, for example, by vibrations, can act only on one of the three parts in the sense of opening.
The high holding forces which hold the holding device in the rest position of the component in case of an accident situation should not lead to an overly long reaction time. Therefore, in the known holding device, the ratchet arrangement with a ratchet kinematics is made as a reducing gear, specifically as a lever gear. The electromagnet acts on the long lever arm of the second ratchet.